(1) Field of the Invention
The present invention relates to a cleaning device for cleaning a toner image bearer that supports a toner image formed by electrophotography as well as relating to an image forming apparatus using the same device.
(2) Description of the Prior Art
Conventionally, the image forming apparatus performs electrographic image forming in the following process. First, in the charging step, a rotationally driven photoreceptor drum is electrified by a charger. In the light illumination step, an electrostatic latent image is formed on the photoreceptor drum by illumination of light in accordance with image information. In the toner image forming step, a toner image is formed by adhering toner to the electrostatic latent image by a developing device. In the transfer step, this toner image is transferred via an intermediate transfer medium or directly to a recordingmedium such as a sheet material, paper or the like, to produce an image output.
As for the photoreceptor drum (toner image bearer) on which toner images are formed by the charging, light illuminating and toner image forming steps, the developed image information (toner image) on the photoreceptor drum will not be completely transferred to the paper or the intermediate transfer medium in the transfer stage. The transfer efficiency is usually and roughly estimated to be 85 to 95%, though this depends on the apparatus and the transfer device.
The toner thus left over on the photoreceptor drum remains adhering on the photoreceptor drum after the transfer step, and would exert an adverse effect on the next image forming and degrade print quality.
To deal with this, there has been a conventionally known configuration in which a cleaning device is disposed at a peripheral part of the photoreceptor drum on the downstream side of the transfer station where the toner image is transferred to the intermediate transfer medium, the paper or the like so that the surface of the photoreceptor drum is cleaned by collecting the leftover toner on the photoreceptor drum after transfer of the toner image to the transfer medium and the gathered residual toner is collected into a waste toner box.
For example, the cleaning device disclosed in Patent Document 1 shown below as a prior art technology, includes a cleaning blade for removing residual toner on the photoreceptor drum surface, a film disposed under the cleaning blade to receive the removed residual toner (waste toner) and a waste toner conveying screw for conveying the waste toner and is designed to easily collect waste toner by placing and vibrating the film by putting into contact with the waste toner conveying screw.
However, in the cleaning device disclosed in Patent Document 1, since the film and the waste toner conveying screw come into contact with each other in a large contact area, which increases the load for driving the waste toner conveying screw, there occur other problems such as increase of the driving torque of the motor for driving the waste toner conveying screw and increase in consumption current.
To deal with this, a cleaning device for solving the above problems has been disclosed in Patent Document 2 shown below. The cleaning device disclosed in Patent Document 2 includes a vibrating part formed of a film sheet having a plurality of vanes, which each are formed of a plane with its width laid out approximately perpendicular to the axial direction of the waste toner conveying screw. This vibrating part is arranged between the cleaning blade and the waste toner conveying screw, close to the cleaning blade with the plurality of vanes in abutment with the auger of the waste toner conveying screw. Further, in the cleaning device disclosed in Patent Document 2, the pitch between the vanes and the pitch of the waste toner conveying screw are made different so that the vanes that abut the waste toner conveying screw change as the waste toner conveying screw rotates, whereby the vanes vibrate when the vanes are released to recover their original state from the state of abutment between the vanes and the waste toner conveying screw, which, in turn, vibrate the waste toner on the cleaning blade near the vanes. In this way, in the cleaning device disclosed in Patent Document 2, the increase of the load on the drive motor for driving the waste toner conveying screw can be suppressed by avoiding constant contact between the vibrating part and waste toner conveying screw, to realize energy saving with a lower increase in consumption current.
In the thus configuration cleaning device disclosed in Patent Document 2, collection of the waste toner from the cleaning blade can be promoted by application of vibrations with the vibrating part, it is hence possible to keep the surface of the toner image bearer constantly clean by effecting a fair cleaning function without causing any stagnation of waste toner around the cleaning blade.
[Prior Art Documents]
    Patent Document 1:
Japanese Patent Application Laid-open No. S58-144873    Patent Document 2:
Japanese Patent Application Laid-open No. 2009-109830
However, it is impossible for the vibrating member of Patent Document 2 to stir the waste toner near the photoreceptor drum. In particular, there has been the problem that the waste toner near the photoreceptor drum immediately before passage of the cleaning blade cannot be removed clean enough.